TADFNIR · High performance OLEDs using deep red (DR) and near-infrared (NIR) TADF emitters
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2020-11-02 → 2022-11-11
- EU contribution
- €212,934
- Participants
- 1
- Scheme
- MSCA-IF
Lines connect the coordinator with its partners.
Results in brief
High performance OLEDs using deep red (DR) and near-infrared (NIR) TADF emitters
Organic light-emitting diodes (OLEDs) are widely used in niche lighting, smartphones, televisions/displays, watches and automotive displays, smart phones, wearable electronics, and solid-state lighting applications, owing to their phenomenal performances, including fast response time, wide viewing angles, thinner display, better contrast ratio, low power consumption, lightweight and exciting optical and electrical properties. Commercial OLEDs still rely on expensive and rare metal iridium (cost – US$5400/Oz, global production 3 tonnes per annum). Therefore, the development of economical and sustainable emitters for the replacement of expensive metal-based emitters is indispensable. Recent years have witnessed that thermally activated fluorescence (TADF) materials could be an alternative solution to expensive metal-based emitters. The remarkable features of TADF materials are that they can achieve 100% IQE, while maintaining a facile color-tuning ability. To date, numerous TADF materials have been reported and exploited in fabricating sky blue, green, and red OLEDs. Deep red (DR) and near-infrared (NIR) emissive materials (650 nm to 750 nm) have occupied special attention given their potential in applications such as night vision devices, optical communication etc. Though osmium, iridium, or platinum complexes are known to exhibit long wavelength emission, they suffer from large efficiency roll-offs at high current densities, making them largely unsuitable for such commercial applications. The developments of TADF-based DR/NIR materials are not in pace with other color TADF emitters because of their low photoluminescence quantum yields and OLED device performances. We have addressed the low photoluminescence quantum yields of emitters of DR/NIR TADF materials by adopting (i) a rigid and strong acceptor strategy, (ii) aggregation-induced emission active unit incorporation into the deep red TADF emitter. We obtained moderate PLQY values and then employed these emitters in OLEDs. In the course of our efforts, we discovered and assessed the potential of a weak electron donor for use in blue TADF emitter design.
Data: CORDIS, © European Union
Project objective
First-generation fluorescent and second-generation phosphorescent organic light-emitting diodes (OLEDs) can achieve maximum internal quantum efficiency (IQE) of 25% and 100%, respectively. Phosphorescent OLEDs with complexes based on iridium and platinum realize 100% IQE due to the heavy atom effect. However, there are limitations, including but not limited to their scarcity and toxicity profile. The third generation OLEDs based on a thermally activated delayed fluorescence (TADF) process can be realized in purely organic materials and produce devices with 100% IQE. So far, there are examples of high-performance blue, green and red TADF OLEDs; however, limited attention has been paid to deep red (DR) and near-infrared (NIR) TADF emitters (650-750 nm). Such DR and NIR emitters find applications in night vision displays, sensors and information-secured displays etc. Current NIR OLEDs are associated with issues related to efficiency roll-off, lifetime and purity of emission color. Most importantly, the materials contain osmium, iridium, or platinum metals and therefore these OLEDs suffer from the same issues as visible light phosphorescent counterparts. This proposal seeks to address the above issues by rational design of purely organic novel DR and NIR TADF emitters. Our design comprises of yet unexplored rigid anthrone-based strong electron acceptor decorated with suitably substituted donor carbazoles. Emission color tunability can be achieved as a function of donor choice and position and varying the strengths of either the donor or acceptor. The rigidity of the molecular components, the strengths of the acceptor/donor, the twisted conformation, and the presence of tertiary butyl groups on the carbazoles altogether will work coherently to furnish good device stability, reduced efficiency roll-off, narrow emission spectra and an improved lifetime of the OLEDs. Overall, this proposal is anticipated to provide a major breakthrough in DR and NIR TADF emitters.
Original text from CORDIS.
Participants
- THE UNIVERSITY COURT OF THE UNIVERSITY OF ST ANDREWS · ST ANDREWSCoordinatorUnited Kingdom
Links
Data: CORDIS, © European Union